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Add BufFileRead variants with short read and EOF detection

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Most callers of BufFileRead() want to check whether they read the full
specified length.  Checking this at every call site is very tedious.
This patch provides additional variants BufFileReadExact() and
BufFileReadMaybeEOF() that include the length checks.

I considered changing BufFileRead() itself, but this function is also
used in extensions, and so changing the behavior like this would
create a lot of problems there.  The new names are analogous to the
existing LogicalTapeReadExact().

Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/f3501945-c591-8cc3-5ef0-b72a2e0eaa9c@enterprisedb.com
This commit is contained in:
Peter Eisentraut
2023-01-16 09:20:44 +01:00
parent 1561612e3b
commit 20428d344a
9 changed files with 73 additions and 134 deletions
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9
src/backend/utils/sort/logtape.c
View File

@@ -281,19 +281,12 @@ ltsWriteBlock(LogicalTapeSet *lts, long blocknum, const void *buffer)
static void
ltsReadBlock(LogicalTapeSet *lts, long blocknum, void *buffer)
{
size_t nread;
if (BufFileSeekBlock(lts->pfile, blocknum) != 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not seek to block %ld of temporary file",
blocknum)));
nread = BufFileRead(lts->pfile, buffer, BLCKSZ);
if (nread != BLCKSZ)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read block %ld of temporary file: read only %zu of %zu bytes",
blocknum, nread, (size_t) BLCKSZ)));
BufFileReadExact(lts->pfile, buffer, BLCKSZ);
}
/*

49
src/backend/utils/sort/sharedtuplestore.c
View File

@@ -422,23 +422,10 @@ sts_read_tuple(SharedTuplestoreAccessor *accessor, void *meta_data)
*/
if (accessor->sts->meta_data_size > 0)
{
if (BufFileRead(accessor->read_file,
meta_data,
accessor->sts->meta_data_size) !=
accessor->sts->meta_data_size)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from shared tuplestore temporary file"),
errdetail_internal("Short read while reading meta-data.")));
BufFileReadExact(accessor->read_file, meta_data, accessor->sts->meta_data_size);
accessor->read_bytes += accessor->sts->meta_data_size;
}
if (BufFileRead(accessor->read_file,
&size,
sizeof(size)) != sizeof(size))
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from shared tuplestore temporary file"),
errdetail_internal("Short read while reading size.")));
BufFileReadExact(accessor->read_file, &size, sizeof(size));
accessor->read_bytes += sizeof(size);
if (size > accessor->read_buffer_size)
{
@@ -455,13 +442,7 @@ sts_read_tuple(SharedTuplestoreAccessor *accessor, void *meta_data)
this_chunk_size = Min(remaining_size,
BLCKSZ * STS_CHUNK_PAGES - accessor->read_bytes);
destination = accessor->read_buffer + sizeof(uint32);
if (BufFileRead(accessor->read_file,
destination,
this_chunk_size) != this_chunk_size)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from shared tuplestore temporary file"),
errdetail_internal("Short read while reading tuple.")));
BufFileReadExact(accessor->read_file, destination, this_chunk_size);
accessor->read_bytes += this_chunk_size;
remaining_size -= this_chunk_size;
destination += this_chunk_size;
@@ -473,12 +454,7 @@ sts_read_tuple(SharedTuplestoreAccessor *accessor, void *meta_data)
/* We are now positioned at the start of an overflow chunk. */
SharedTuplestoreChunk chunk_header;
if (BufFileRead(accessor->read_file, &chunk_header, STS_CHUNK_HEADER_SIZE) !=
STS_CHUNK_HEADER_SIZE)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from shared tuplestore temporary file"),
errdetail_internal("Short read while reading overflow chunk header.")));
BufFileReadExact(accessor->read_file, &chunk_header, STS_CHUNK_HEADER_SIZE);
accessor->read_bytes = STS_CHUNK_HEADER_SIZE;
if (chunk_header.overflow == 0)
ereport(ERROR,
@@ -489,13 +465,7 @@ sts_read_tuple(SharedTuplestoreAccessor *accessor, void *meta_data)
this_chunk_size = Min(remaining_size,
BLCKSZ * STS_CHUNK_PAGES -
STS_CHUNK_HEADER_SIZE);
if (BufFileRead(accessor->read_file,
destination,
this_chunk_size) != this_chunk_size)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from shared tuplestore temporary file"),
errdetail_internal("Short read while reading tuple.")));
BufFileReadExact(accessor->read_file, destination, this_chunk_size);
accessor->read_bytes += this_chunk_size;
remaining_size -= this_chunk_size;
destination += this_chunk_size;
@@ -551,7 +521,6 @@ sts_parallel_scan_next(SharedTuplestoreAccessor *accessor, void *meta_data)
if (!eof)
{
SharedTuplestoreChunk chunk_header;
size_t nread;
/* Make sure we have the file open. */
if (accessor->read_file == NULL)
@@ -570,13 +539,7 @@ sts_parallel_scan_next(SharedTuplestoreAccessor *accessor, void *meta_data)
(errcode_for_file_access(),
errmsg("could not seek to block %u in shared tuplestore temporary file",
read_page)));
nread = BufFileRead(accessor->read_file, &chunk_header,
STS_CHUNK_HEADER_SIZE);
if (nread != STS_CHUNK_HEADER_SIZE)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from shared tuplestore temporary file: read only %zu of %zu bytes",
nread, STS_CHUNK_HEADER_SIZE)));
BufFileReadExact(accessor->read_file, &chunk_header, STS_CHUNK_HEADER_SIZE);
/*
* If this is an overflow chunk, we skip it and any following

29
src/backend/utils/sort/tuplestore.c
View File

@@ -1468,15 +1468,11 @@ getlen(Tuplestorestate *state, bool eofOK)
unsigned int len;
size_t nbytes;
nbytes = BufFileRead(state->myfile, &len, sizeof(len));
if (nbytes == sizeof(len))
nbytes = BufFileReadMaybeEOF(state->myfile, &len, sizeof(len), eofOK);
if (nbytes == 0)
return 0;
else
return len;
if (nbytes != 0 || !eofOK)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from tuplestore temporary file: read only %zu of %zu bytes",
nbytes, sizeof(len))));
return 0;
}
@@ -1528,25 +1524,12 @@ readtup_heap(Tuplestorestate *state, unsigned int len)
unsigned int tuplen = tupbodylen + MINIMAL_TUPLE_DATA_OFFSET;
MinimalTuple tuple = (MinimalTuple) palloc(tuplen);
char *tupbody = (char *) tuple + MINIMAL_TUPLE_DATA_OFFSET;
size_t nread;
USEMEM(state, GetMemoryChunkSpace(tuple));
/* read in the tuple proper */
tuple->t_len = tuplen;
nread = BufFileRead(state->myfile, tupbody, tupbodylen);
if (nread != (size_t) tupbodylen)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from tuplestore temporary file: read only %zu of %zu bytes",
nread, (size_t) tupbodylen)));
BufFileReadExact(state->myfile, tupbody, tupbodylen);
if (state->backward) /* need trailing length word? */
{
nread = BufFileRead(state->myfile, &tuplen, sizeof(tuplen));
if (nread != sizeof(tuplen))
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from tuplestore temporary file: read only %zu of %zu bytes",
nread, sizeof(tuplen))));
}
BufFileReadExact(state->myfile, &tuplen, sizeof(tuplen));
return (void *) tuple;
}